1. Field of the Invention
The invention relates to wireless devices that conforms to the 1999 IEEE 802.11 standard or the updated 2003 IEEE 802.11 standard. Specifically, the invention relates to ensuring that such wireless devices also conform to the regulations governing such wireless devices in various countries worldwide.
2. Description of the Related Art
Many devices currently have the capability to communicate without the use of a wired network. Such devices can include, for example, laptops and personal digital assistants (PDAs). These devices can use a wireless local area network (WLAN), which can operate separately from or operate in conjunction with an existing wired network.
Wireless communication can be characterized by two modes of operation: an infrastructure mode and an ad hoc mode. FIG. 1A illustrates an infrastructure mode, wherein an access point AP1 communicates with a plurality of clients C1, C2, and C3. Note that in order for client C1 to communicate with client C3 in infrastructure mode, client C1 must communicate via access point AP1. Thus, access point AP1 functions as a communication hub between clients C1, C2, and C3.
Access point AP1 also serves as a gateway for clients C1, C2, and C3 to communicate with clients not associated with access point AP1. For example, access point AP1 can communicate with another access point, such as access point AP2, which in turn can be associated with a plurality of clients C4 and C5. Because a client can be a mobile device and each access point has a predetermined range of service, a client may associate with an access point for a first time period and then associate with another access point for a second time period. For example, client C3, which is communicating with client C2, could at some time be outside the range of access point AP1. At this point, client C3 could disassociate from access point AP1 and associate with access point AP2, as indicated by dashed lines, thereby ensuring that its communication to client C2 is maintained.
In contrast, FIG. 1B illustrates an ad hoc mode, wherein clients C1, C2, and C3 can communicate directly without an access point. In this mode, each client would have access to the resources of the other clients, but not to the resources of an access point, which typically includes a central server. Therefore, communication in the infrastructure mode can generally support more complex and volume intensive use.
The IEEE 802.11d standard, which was published as a supplemental standard in 2001, provides a beacon format to be used in the infrastructure mode. Specifically, an AP normally broadcasts an information element (i.e. a beacon), which includes information for identifying and defining the wireless network, such as its name and security level. Additionally, the information element may include information regarding country, regulatory domain, frequency, and power levels. This type of information element is called an 802.11d beacon herein.
However, the 802.11d standard fails to define a protocol on how to use this information or what to do when this information is imperfect, incomplete, or simply not applicable to the product that receives it. For example, if the client product is an 802.11a product (operating at 5 GHz) and is operating near an AP broadcasting an 802.11d beacon for an 802.11b product (operating at 2.4 GHz), then the client product is unlikely to respond at all or, alternatively, might not respond to the beacon in a permissible manner (thereby risking a product ban or other import/financial penalties in that country). Therefore, a need arises for a client product to determine where it is and to operate properly in both infrastructure and ad hoc modes, even when the information element provides information that is imperfect, incomplete, or different than anticipated.